Oxidation of alkyl aromatics

ABSTRACT

Process of liquid phase oxidation of the alpha carbon atom of alkylbenzenes by a manganic or cobaltic salt and an acid activator with or without an oxidation-resistant solvent either in an inert atmosphere to produce lower oxidation products of the alpha carbon atom such as alcohols or their esters; or, in the presence of molecular oxygen, to produce higher oxidation products such as aromatic aldehydes, ketones or carboxylic acids.

United States Patent de Radzitzky dOstrowick et al.

[451 May 23, 1972 154] OXIDATION OF ALKYL AROMATICS [72] Inventors: Pierre de Radzitzky dOstrowick; Jacques D. V. Hanotier, both of Brussels, Belgium [52] US. Cl ..260/488 CD, 260/524 M, 260/592, 260/599, 260/600, 260/613 D, 260/618 C [51] Int. Cl. ..C07c 47/54, C07c 63/02, C07c 69/14 [58] Field of Search ..260/524 M, 524 R, 488 CD, 618 C [5 6] References Cited UNITED STATES PATENTS 2,245,528 6/1941 Loder ..260/524 FOREIGN PATENTS OR APPLICATIONS 143,392 5/l920 Great Britain ..260/524 17,982 8/1904 Great Britain ..260/524 Primary Examiner]ames A. Patten Assistant ExaminerR. S. Weissberg Att0rneySol B. Wiczer and M. N. Cheairs [57] ABSTRACT Process of liquid phase oxidation of the alpha carbon atom of alkylbenzenes by a manganic or cobaltic salt and an acid activator with or without an oxidation-resistant solvent either in an inert atmosphere to produce lower oxidation products of the alpha carbon atom such as alcohols or their esters; or, in the presence of molecular oxygen, to produce higher oxidation products such as aromatic aldehydes, ketones or carboxylic acids.

25 Claims, No Drawings OXIDATION OF ALKYL AROMATICS The present invention relates to a process for selective oxidation of alkylaromatic compounds using an oxidizing system comprising a higher valent cobalt(lII) or manganese(lH) salt of a carboxylic acid and a relatively strong acid.

Oxidation of alkylaromatic compounds into oxygenated products in the liquid phase with molecular oxygen in the presence of a heavy metal catalyst is the best available to the chemical industry at this time. Its application remains restricted as a rule to the production of carboxylic acids. This is principally due to the fact that to reach a sufficient rate of reaction, stringent conditions such as high temperatures and pressures must be applied so that intermediate oxidation products of the alcohol aldehyde or ketone type are rapidly converted into acids. During this process, the alkyl groups comprising several atoms of carbon undergo a cleavage of the carbon-carbon bonds except for those joining these to the aromatic nucleus. For this reason, the method is applied principally for oxidation of methylaromatic hydrocarbons like toluene and xylenes. Oxidations performed in the art under milder conditions with various catalysts have been non-selective or inapplicable.

We have now discovered that by employing an oxidizing system comprising the cobalt or manganese salt of a carboxylic acid in higher valent form and a relatively strong acid, the oxidation of the alkylaromatic compounds can be performed at distinctly lower temperatures than those previously required, with a higher rate of reaction and a greatly improved selectivity. We have found, that by appropriate selection of the components of the oxidizing system and of the operating conditions, the oxidation of the alkylaromatic compounds can be controlled to form side chain alcohols, mainly in the form of esters; or to form aromatic ketones or aldehydes, depending on the structure of the alkyl substituent; or to form aromatic carboxylic acids selectively as principal products. Analogously, starting with a polyalkylated aromatic compound, the reaction can be limited to selectively oxidize a single alkyl group or carried further to oxidize several alkyl side chains. Finally, the oxidizing system employed has an activity such that the alkylaromatic compounds further substituted by a deactivating group are attacked rapidly. Such deactivating groups are chloro, nitro, carboxyl or other electron-attracting groups.

The main object of the present invention is to provide a process for the oxidation of alkylaromatic compounds, during which one or more alkyl groups thereof are converted quickly in satisfactory yield into oxygenated functions, with a high degree of selectivity and control. It is a further object to provide u process of carrying out such oxidations at low temperalures.

According to the present invention, alkylaromatic compounds having at least one hydrogen atom at the alpha position to the aromatic nucleus are oxidized in the liquid phase at that alpha position at a temperature in the range of 30 to +lO C., with an oxidizing system comprising the higher valent cobalt(IlI) or higher valent manganese(lIl) salt of a carboxylic acid and a stable acid whose dissociation constant is higher than or boron trifluroide, or a mixture thereof.

The alkylaromatic compounds which are oxidized most satisfactorily by the process of the invention are those which comprise at least one alkyl radical having at least one hydrogen atom at the alpha position relative to the aromatic ring. Although higher alkyl radicals can be oxidized such as those having up to about 30 carbon atoms or even higher, the aromatic compounds with l to 6 alkyl radicals having from one to four carbon atoms are a preferred group of alkylaromatic compounds to be oxidized since they are easily and more economically available. Typical alkylaromatics oxidized herein are the mono-, diand tri-alkylbenzenes, like toluene, ethylbenzene, cumene, 0-, mor p-xylenes, o-, mor pdiethylbenzenes and trimethyl benzenes. Polynuclear alkylaromatic compounds such as the mono-, diand trialkylnaphthalenes, like methyl naphthalenes, ethyl naphthalenes and dimethylnaphthalenes are also easily oxidized. Apart from these purely hydrocarbon compounds, alkylaromatic compounds substituted by other radicals, for example chloro, bromo, iodo, fluoro, nitro or oxygenated radicals such as acyl, alkoxy, carboxyl, l-acyloxyalkyl, may also be oxidized. Typical such substituted alkylaromatic compounds are pchlorotoluene, p-bromoethylbenzene, m-nitrotoluene, oacetyltoluene, 4-methoxyethylbenzene, p-toluic acid, 4- methyl-l-naphthoic acid, p-methylbenzyl acetate, and the like.

In order that the oxidation of these compounds by the process of the invention may be performed in the liquid phase, it is not essential, but often useful, to employ a solvent. In particular cases, the oxidizing system is soluble in the liquid alkylaromatic compound to be oxidized, and the reaction can occur in the solution thus obtained. Most frequently, however, the reactants are desirably dissolved in a solvent common to both. In general any liquid reasonably inert to oxidation, in which the alkylaromatic compound to be oxidized and the oxidizing system are soluble, may be used. The fatty acids containing from two to 10 carbon atoms and their lower esters, preferably their methyl and t-butyl esters; satisfactorily fulfill the preceding conditions. Acetic acid is a particularly advantageous solvent.

Among the metal compounds capable of oxidizing hydrocarbon or other organic substances, the cobalt(lII) and manganese(lll) salts of carboxylic acids are preferred. They are powerful oxidizers; they are satisfactorily soluble in such organic solvents; they are easily produced by known methods. From these points of view, the cobalt(III) and manganese(lll) salts of fatty acids containing from 2 to 10 atoms of carbon, and preferably their acetates, are particularly satisfacory. For example, cobalt(lll) acetate may be produced by cooxidation of cobalt( II) acetate with acetaldehyde in acetic acid in the presence of oxygen. Manganeseflll) acetate may be produced by oxidation of manganese() acetate with potassium permanganate in acetic acid. The cobalt(lll) and manganese( Ill) salts of the other fatty acids can be produced in analogous manner or by exchange reaction between these and cobalt( Ill) acetate.

A fundamental and important aspect of the present invention is the discovery that the oxidizing power of these cobaltic and manganic salts in respect of alkylaromatic compounds is enhanced considerably by the presence of a relatively strong inorganic or organic acid. The acids which display this activating effect are those whose dissociation constant K is higher than 10 They should be soluble in the reaction medium and should not interfere with the reaction. Suitable acids are sulphuric acid (K, perchloric acid (K I), p-toluenesulphonic acid (K L l), lrilluoroucclic acid (I\'-= 6.10 trichlorozlcclic acid (K= 2.10 dichloruacetic acid (K 3.3 X 10*), phosphoric acid (K,=7.5 X l() and monochloroacetic acid (K= l.4 IO). Some Lewis acids such as boron trifluoride, also have an activating action. The acids containing chlorine, bromine or iodine in ionic form, such as hydrochloric acid, hydrobromic acid or aluminium trichloride are unstable in the conditions of the process and should be avoided.

The activating action of the acids defined above is exerted both on the rate and the progress of the reaction. The effect is the more pronounced the stronger the acid and, up to a definite limit, the higher its concentration. On the other hand, the quantity of acid should be correlated to the quantity of cobaltic or manganic salt employed. For example, if sulphuric acid is employed to activate a cobaltic salt, a molar ratio between acid and salt of approximately 2 is needed to reach maximum activity. With an acid of lesser strength, such as trichloroacetic acid, a ratio from 5 to 20 is preferable. Although the mechanism of the activation has not been clarified yet, the facts which have been set forth lead to the possibility that the cobaltic or manganic salt reacts with the acid to produce a more oxidizing species which is assumed to Y be principally responsible for the attack of the substrate. The

following scheme can be envisaged accordingly, where the acid, the metal salt and the reactive species are represented respectively by AH, M and M(lll) M l-l* M(lll) 2 It must be added, moreover, that the activating effect of a given acid can vary with temperature, the nature of the metal salt and the reactivity of the substrate. For example, the activating action of weaker acids such as trichloroacetic acid on manganic acetate is less efi'ective, under identical conditions, than on cobaltic acetate; but, at increased temperature, it is improved the more effectively with the more reactive substrate. These different factors should be taken into account in selecting the oxidizing system and the conditions to apply to oxidize a particular substrate.

The activator allows the oxidation of alkylaromatics to be performed at low temperature, more specifically within a temperature range of -30 to 100 C. In order that the reaction may be rapid as well as selective, it is preferable to operate at temperatures between and 60 C. The reaction will frequently be too slow below 0 C., and the selectivity inadequate above 60 C.

The nature of the oxidation products obtained by the present process is determined by the structure of the alkyl substituent, the composition of the oxidizing system, and the operating conditions. To produce alcohols in the form of esters, the reaction will be carried out in a carboxylic solvent such as acetic acid and in the absence of oxygen. For example, in these conditions, ethylbenzene can be converted almost quantitatively into the acetate of alpha-methylbenzyl alcohol by use of an oxidizing system comprising a manganic or a cobaltic salt. The ester obtained may then be hydrolyzed to produce the corresponding alcohol, or pyrolyzed to produce styrene. Toluene is converted into benzyl acetate using the same conditions. By contrast, if it is preferred to obtain products containing a carbonyl function, it is advisable to operate in the presence of oxygen and to make provision for vigorous stirring of the reaction mixture. In these conditions, ethylbenzene can be converted into acetophenone by preferential use of an oxidizing system comprising a cobaltic salt. Analogously, in the presence of oxygen, toluene can be oxidized into benzaldehyde or benzoic acid, depending on whether a manganic or cobaltic salt is employed. These particular examples clearly demonstrate the extraordinary selectivity of the process of the invention and the high degree of control it provides by simple selection of the oxidizing system and of the operating conditions.

The effect of oxygen exemplified by the above instances is another important aspect of the present invention. The manner in which oxygen operates in the reaction is not known with certainty. in the prior processes in which a compound of a metal of high valency is employed as an oxidant, oxygen does not as a rule have an appreciable effect on the reaction. In the present case, it seems that the primary attack of the alkylaromatic compound leads to the formation of a free radical (reaction 3) which would then react with oxygen (reaction 4) to produce a peroxy radical which is subsequently convertible to produce a ketone, an aldehyde or even an acid, as the case may be. in theabsence of oxygen, the radical would be oxidized in its turn, probably while producing a carbonium salt (reaction 5) which, in the presence of a carboxylic acid, would result in an ester (reaction 6) R 0 ROO ketone, aldehyde or acid R R'COOl-l RCOOR l-l (6) Corresponding to this pattern, the proportion of ester functions and of carbonyl functions in the reaction products is the result of competition between reactions (4) and (5). It will then be grasped that to promote the production of compounds having a carbonyl function, it is necessary to choose conditions allowing the reaction (4) to predominate, that is to say to operate in the presence of a gaseous phase containing oxygen and to make provision for vigorous stirring for rapid diffusion of the same into the liquid phase. This gaseous phase may con sist of pure oxygen or of a mixture of oxygen with other gases which are inert in the conditions of the reaction, for example air. The partial oxygen pressure may be between 0.1 and 50 atmospheres. In particular cases, it is possible to apply pressures lying outside this range. For example, a lower pressure than 0.] atmosphere can be sufficient occasionally, subject to the condition of providing particularly effective stirring. On the other hand, higher pressures than 50 atmospheres may be applied, but these do not lead to an improvement in the results justifying additional plant investment costs. In the greater number of cases, an oxygen pressure of the order of 0.2 to 10 atmospheres will suffice to secure a high degree of conversion into products having a carbonyl function.

The quantity of oxydant to be employed depends on the degree of conversion required and on the nature of the products it is desired to obtain. The preceding pattern shows that at least two molar equivalents of higher valent metal salts are needed to produce an ester in a high yield from a mono-alkylbenzene. It might have been expected that a greater quantity of oxydant would be consumed to produce a ketone, an aldehyde or an acid. In reality, the production of these compounds by the process of the invention requires no more than a small quantity of oxidant. For example, the production of acetophenone by oxidation of ethylbenzene by means of the system consisting of cobaltic acetate and trichloroacetic acid in the presence of oxygen requires no more than 1.5 to 2.2 atoms of cobalt( 111) per molecule of hydrocarbon. in the same conditions, 0.3 to 0.5 atom of cobalt(lll) suffices to convert one molecule of toluene into benzoic acid. These small values demonstrate that a definite degree of regeneration of the oxidizing system occurs in the presence of oxygen, so that the quantity of oxidant consumed may in particular cases be smaller than the quantity of product formed.

In the case of polyalkyl aromatic compounds, the oxidation may be limited to a single alkyl group, or extended to several. It is plain to one versed in the art that, to limit the oxidation, it is appropriate to shorten the period of reaction and to employ an excess of polyalkyl benzene in comparison with the oxidizing system, whereas the inverse of these conditions will be preferable if it is desired to oxidize several alkyl groups within one and the same molecule.

The invention will now be further described with reference to the following examples EXAMPLE 1 This example illustrates the effect of sulphuric acid on the oxidizing power of manganic acetate with respect to alkylaromatic compounds.

A solution containing 0.20 mol/liter of m-diethylbenzene and 0.04 mol/liter of manganic acetate in acetic acid was heated to 70 C. for 30 minutes. In a second assay, sulphuric acid was added to the solution at the concentration of 0.5 mol/liter, after which this solution was kept at 25 C. for 10 minutes. A third assay was also carried out in the presence of sulphuric acid but in the absence of substrate. At the end of the three assays, the manganic ions present in the solution were determined by cerimetry. The results obtained are given in the following table.

Substrate H,S0 Temperature Time reduced Mn(lll) (0.20M) (0.5M) (0 C) (min) (70) It is apparent that, in the presence of sulphuric acid, the oxidation of m-diethylbenzene by manganic acetate results in the almost complete reduction of the same in 10 minutes at 25 C., whereas in the absence of sulphuric acid, no appreciable reaction occurs in distincly more severe conditions. The third assay adequately demonstrates that the effect of the activator is linked with the presence of m-diethylbenzene.

EXAMPLE II This example illustrates the effect of trichloroacetic acid on the oxidizing power of cobaltic acetate in respect of alkylaromatic compounds. A solution containing 0.20 mol/liter of 2- ethylnaphthalene and 0.05 mol/liter of cobaltic acetate in acetic acid was kept at 25 C. under a nitrogen atmosphere at atmospheric pressure for 15 minutes. The same assay was repeated after addition of trichloroacetic acid to the solution, in the proportion of 1.5 mol/liter. A third assay was also carried out in the presence of trichloroacetic acid, but in the absence of substrate. At the end of the three assays the cobaltic ions present in the solution were determined by cerimetry. The results obtained are given in the following table substrate trichloroacetic acid reduced Co(lll) It is apparent that in the presence of trichloroacetic acid the oxidation of 2-ethylnaphthalene by means of cobaltic acetate results in the almost complete reduction of the same, whereas no appreciable reaction occurs in the absence of the acid ac tivator. The third assay adequately shows that its action is linked to the presence of the hydrocarbon.

EXAMPLE III This example illustrates the oxidation of toluene by means of the system consinsting of manganic acetate and sulphuric acid.

A solution containing 0.10 mol/liter of toluene, 0.21 mol/liter of manganic acetate and 1.0 mol/liter of sulphuric acid in acetic acid, was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 78 percent of the manganic ions had been reduced after 1 hour. An aliquot part of the reaction mixture was diluted with ether and then treated at C. with anhydrous sodium carbonate until the acidity was neutralized. The ether solution was analyzed by vapor phase chromatography to establish the composition of the neutral oxidation products. The acid products were identified by analysis of another aliquot part of the reaction mixture. The combined results of both analyses show that 54 percent of the toluene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages benzyl alcohol (mainly in the form ofits acetate ester) 74% benzaldehyde 25% benzoic acid 1% EXAMPLE IV This example illustrates the effect of oxygen on the oxidation of toluene by means of the oxidizing system employed in the preceding example.

The experiment of Example III was repeated, but this time while stirring the reaction mixture in the presence of pure oxygen at atmospheric pressure. By treating and analyzing the reaction mixture as in Example III, it was established that 65 percent of the toluene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages benzaldehyde 71% benzyl alcohol (mainly in the form of its acetate ester) 24% benzoic acid 5% Comparing the results of this example to those of Example 111, it is plain that in the presence of oxygen, toluene is converted preferentially into benzaldehyde rather than into benzyl alcohol.

EXAMPLE V This example illustrates the oxidation of toluene by means of the system consisting of cobaltic acetate and trichloroacetic acid, in the presence of oxygen.

A solution containing 0.10 mol/liter of toluene, 0.20 mol/liter of cobaltic acetate and 1.5 mol/liter of trichloroacetic acid in acetic acid was stirred at 25 C. in the presence of pure oxygen at atmospheric pressure. 16 percent of the cobaltic ions had been reduced after 4 hours. The reaction mixture was then treated and analyzed as in Example 111. It was found that 81 percent of the toluene employed had been converted into pure benzoic acid.

In another experiment performed in identical manner but while extending the reaction period to 24 hours, the conversion of toluene into benzoic acid rose to 92 percent.

From this data it is calculated that the formation of a molecule of benzoic acid required the reduction of no more than 0.3 atom of cobalt, which demonstrates that a substantial proportion of the oxidant is regenerated in situ" during the reaction.

EXAMPLE VI This example illustrates the use of propionic acid as a solvent.

The experiment of the preceding example was repeated, while replacing acetic acid with propionic acid. Analysis of the reaction mixture after 24 hours showed that 55 percent of the toluene employed had been converted mainly to yield benzoic acid (98 percent) and small quantities of benzaldehyde (2 percent) Identical results were obtained by replacing cobaltic acetate with cobaltic propionate.

EXAMPLE VII This example illustrates the oxidation of ethylbenzene by means of the system consisting of manganic acetate and sulphuric acid.

A solution containing 0.10 mol/liter of ethylbenzene, 0.19 moi/liter of manganic acetate and 1.0 mol/liter of sulphuric acid in acetic acid was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 67 percent of the manganic ions had been reduced after 1 hour. The reac tion mixture was then treated and analyzed as in Example III. It was thus established that 56 percent of the ethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages.

alpha-methylben2yl alcohol (mainly in the form of its acetate ester) 93 acetophenone 7 benzoic acid 0 EXAMPLE VIII This example illustrates the oxidation of ethylbenzene by means of the system consisting of cobaltic acetate and trifluoroacetic acid.

A solution containing 0.10 mol/liter of ethylbenzene, 0.20 mol/liter of cobaltic acetate and 1.4 moi/liter of trifiuoroacetic acid in acetic acid was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 77 percent of the cobaltic ions had been reduced after 24 hours. The reaction mixture was then treated and analyzed as in Example III. It was thus established that 56 percent of the ethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages.

alpha-methylbenzyl alcohol (mainly in the form of its acetate esters) 86 acetophenone 9 benzoic acid 5 By operating in identical manner but omitting the addition of trifluoroacetic acid to the system, only 9 percent of the ethylbenzene was converted to yield the following products alpha-methylbenzyl alcohol acetophenone 67 '70 benzoic acid 33 It is plain that in the absence of the acid activator, the reaction is not only slowed down considerably, but its selectivity is completely changed.

EXAMPLE IX alpha-methylbenzyl alcohol (mainly in the form of its acetate ester) 87 acetophenone benzoic acid 8 By operating in identical manner, but without adding boron triluoride to the system, only 5 percent of the hydrocarbon had been converted to yield the following products alpha methylbenzyl alcohol 0 acetophenone 60 benzoic acid 40 The action of the activator set forth in the preceding example is confirmed in every respect by these results.

EXAMPLE X This example illustrates the oxidation of ethylbenzene by means of the system consisting of cobaltic acetate and ptoluenesulphonic acid.

The experiment of Example VIII was repeated but trifluoroacetic acid was replaced with p-toluenesulphonic acid at the concentration of 0.3 mol/liter. 33 percent of the cobaltic ions had been reduced after 24 hours, and analysis showed that l4 percent of the ethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages alphamethylbenzyl alcohol (mainly in the form ofits acetate ester) 75 70 acetophenone l5 benzoic acid EXAMPLE XI This example illustrates the oxidation of ethylbenzene by means of the system consisting of cobaltic acetate and trichloroacetic acid.

The experiment of Example VIII was repeated but trifluoroacetic acid was replaced with trichloroacetic acid at the same concentration. 25 percent of the cobaltic ions had been reduced after 30 minutes, and analysis showed that I7 percent of the ethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages alpha-methylbenzyl alcohol (mainly in the form of its acetate ester) 88 acetophenone 9 benzoic acid 3 7c EXAMPLE XII The experiment of Example XI was repeated, but operating at 60 C. instead of 25 C. 66 percent of the cobaltic ions had been reduced after 30 minutes, and analysis showed that 40 percent of the ethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages alpha-methylbenzyl alcohol (mainly in the form of its acetate aster) 86 acetophenone 7 benzoic acid 7 7t Compared to those of Example XI, these results show that an increase in the temperature can speed up the reaction without appreciably changing its selectivity.

EXAMPLE XIII This example illustrates the effect of oxygen on the oxidation of ethylbenzene by means of the oxidizing system employed in Examples XI and XII.

A solution containing 0.10 mol/liter of ethylbenzene, 0.20 mol/liter of cobaltic acetate and 1.5 mol/liter of trichloroacetic acid in acetic acid was stirred at 25 C in the presence of pure oxygen at atmospheric pressure. 62 percent of the cobaltic ions had been reduced after four hours. The reaction mixture was then treated and analyzed as in Example III, It was thus established that 67 percent of the ethylbenzene had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages acetophenone 79 alpha-methylbenzyl alcohol (partially in the form of its acetate ester) 15 7: benzoic acid 6 7r By comparing these results to those of Examples XI and XII it is plain that in the presence of oxygen, ethylbenzene is converted mainly into ketone rather than into alcohol.

EXAMPLE XIV The experiment of Example XIII was repeated, but on this occasion operating under an oxygen pressure of IO kglcm Analysis of the reaction mixture after four hours showed that 48 percent of the ethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages acetophenone 84 alpha-methylbenzyl alcohol (partially in the form of its acetate ester) 16 benzoic acid undetectable By comparing these results to those of Example XIII, it is apparent that the proportion of acetophenone has been increased slightly by operating under a higher oxygen pressure. No additional increase is observed, however, if the test is performed under an oxygen pressure of 30 kgjcm EXAMPLE XV This example illustrates the use of methyl acetate as a solvent.

A solution containing 0.l0 mol/liter of ethylbenzene, 0.21 moI/liter of cobaltic acetate and 1.5 mol/liter of trichloroacetic acid in methyl acetate was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 44 percent of the cobaltic ions had been reduced after Shows. The reaction mixture was then treated and analyzed as in Example III. It was thus established that 14 percent of the ethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages alpha-methylbenzyl alcohol (mainly in the form of its acetate ester) 73 acetophenone 22 benzoic acid 5 EXAMPLE XVI This example illustrates the use of t-butyl acetate as a solvent.

The experiment of Example XV was repeated while replacing methyl acetate with t-butyl acetate. 45 percent of the cobaltic ions had been reduced after three hours and analysis showed that 11 percent of the ethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages alpha-methylbenzyl alcohol (mainly in the form of its acetate ester) 82 acetophenone 18 EXAMPLE XVII This example illustrates the use of pelargonic acid as a solvent.

A solution containing 0.51 mol/liter of ethylbenzene, 0.17 mol/liter of cobaltic acetate and 1.5 mol/liter of trichloroacetic acid in pelargonic acid was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 78 percent of the cobaltic ions had been reduced after 24 hours. The reaction mixture was then neutralized by means of alcoholic potash and subjected to saponification for four hours in such manner as to hydrolyze the pelargonic esters formed during the reaction, to facilitate the identification of the oxidation products of ethylbenzene. After filtering the insoluble salts, the alcoholic solution thus obtained was analyzed directly by vapor phase chromatography. The analysis enabled to identify the following oxidation products whose relative proportions are expressed as molar percentages alpha-methylbenzyl alcohol acetophenone EXAMPLE XVIII This example illustrates the possibility of not employing any solvent.

A solution containing 0.2 mol/liter of cobaltic acetate and 1,5 mol/liter of trichloroacetic acid in ethylbenzene was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 59 percent of the cobaltic ions had been reduced after thirty minutes. Analysis of the reaction mixture by a method analogous to that described in Example III enabled to identify the following oxidation products whose relative proportions are expressed as molar percentages acetophenone 67 alpha-methylbenzyl alcohol 31 alpha-methylbenzyl acetate 2 benzoic acid This example also shows that, in the absence of a carboxylic solvent, the formation of ester is negligible, as in the presence of oxygen.

EXAMPLE XIX This example illustrates the oxidation of cumene by means of the system consisting of cobaltic acetate and trichloroacetic acid in the presence of oxygen.

A solution containing 0.10 mol/liter of cumene, 0.20 mol/liter of cobaltic acetate and 1.5 mol/liter of trichloroacetic acid in acetic acid, was stirred at 25 C. in the presence of pure oxygen at atmospheric pressure. 54 percent of the cobaltic ions had been reduced after 24 hours. The

reaction mixture was then treated and analyzed as in Example III. It was thus established that 21 percent of the cumene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages acetophenone 75 alpha, alpha-dimethylbenzyl alcohol 10 benzoic acid 15 EXAMPLE XX This example illustrates the oxidation of Z-ethylnaphthalene by means of the system consisting of cobaltic acetate and trichloroacetic acid.

A solution containing 0.10 mol/liter of 2-ethylnaphtalene, 0.19 mol/liter of cobaltic acetate and 1.5 mol/liter of trichloroacetic acid in acetic acid was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 71 percent of the cobaltic ions had been reduced after 30 minutes. The analysis of the ether extract obtained as described in Example III showed that 57 percent of the 2- ethylnaphthalene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar ercentages 2( l-hydroxyethyl )naphthalene (mainly in the form of its acetate ester) Z-acetylnaphthalene EXAMPLE XXI The experiment of the preceding example was repeated at 0 C. instead of at 25 C., while employing propionic acid instead of acetic acid as a solvent. 43 percent of the cobaltic ions had been reduced after five hours, and analysis showed that 21 percent of the 2ethylnaphthalene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages 2-( l-hydroxyethyl )naphthalene (mainly in the form of its propionate ester) 2-acetylnaphthalene EXAMPLE XXII 2-( l-hydroxyethyl)naphthalene (mainly in the form of its propionic ester) 94 2-acetylnaphthalene 6 EXAMPLE XXIII This example illustrates the oxidation of p-chlorotoluene by means of the system consisting of manganic acetate and sulphuric acid.

A solution containing 0.10 mol/liter of p-chlorotoluene, 0.21 mol/liter of manganic acetate and 1.0 mol/liter of sulphuric acid in acetic acid was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 87 percent of the manganic ions had been reduced after 2 hours. The analysis of the ether extract obtained as described in Example III showed that 62 percent of the p-chlorotoluene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages:

EXAMPLE XXIV This example illustrates the oxidation of p-methoxytoluene by means of the system consisting of cobaltic acetate and trichloroacetic acid.

A solution containing 0.10 mol/liter of p-methoxytoluene, 0.21 mol/liter of cobaltic acetate and 1.5 moi/liter of trichloroacetic acid was kept at 25 C., without stirring, under a nitrogen atmosphere at atmospheric pressure. 88 percent of the cobaltic ions had been reduced after five minutes. The analysis of the ether extract obtained as described in Example III showed that 56 percent of the p-methoxytoluene: employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages p-methoxybenzyl alcohol (mainly in the form of its acetate ester) p-methoxybenzaldehyde EXAMPLE XXV mmitrobenzyl alcohol (mainly in the form of its acetate ester) n-nitrobenzaldehyde EXAMPLE XXVI This example illustrates the oxidation of p-xylene by means of the system consisting of cobaltic acetate and trichloroacetic acid, in the presence of oxygen.

A solution containing 0.05 mol/liter of p-xylene, 0.20 mol/liter of cobaltic acetate and 1.5 moi/liter of trichloroacetic acid was stirred at 25 C. in the presence of pure oxygen at atmospheric pressure. 19 percent of the cobaltic ions had been reduced after 24 hours. The reaction mixture was then diluted with an equal volume of ether. An insoluble residue was filtered, washed for a first time with a mixture of acetic acid and ether (1/1 a second time with water, then dried. The infrared spectrum of the product thus isolated was identical to that of pure terephtalic acid and its acidity amounted to 1 1.98 meq./g. (theoretical value 12.04). On the other hand, the ether filtrates were collected before being treated and analyzed as described in Example III. It was thus established that 59 percent of the p-xylene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages terephtalic acid p-toluic acid EXAMPLE XXVII mixture was then diluted with a saturated solution of sodium chloride in water, then subjected to repeated extractions with ether. The ether extract was neutralized by an aqueous solu tion of sodium carbonate and dried over anhydrous sodium sulphate before being analyzed by vapor phase chromatography. Analysis showed that the total quantity of the mdiethylbenzene employed had been converted, yielding the following oxidation products the relative proportions of which are expressed as molar percentages m-( l-hydroxyethyl )ethylbenzene (mainly in the form of its acetate caster) 78 m-bis( l-hydroxyethyl )benzene (in the form of its diacetate ester) 18 m-ethylacetophenone 4 By operating under the same conditions but omitting sulphuric acid, only 0.2 percent of the manganic ions were reduced after 1 hour (that being twice the time necessary hereinabove) and no oxidation products were detectable by analysis.

EXAMPLE XXVIII The experiment of Example XXVI! was repeated, except that the concentration of manganic acetate was increased by approximately 30 percent (0.28 moi/liter instead of 0.22) and the reaction was extended to a total period of twenty hours. With these conditions, 97 percent of the manganic ions were reduced and the oxidation products were shown to be distributed in mols, in the following manner m-bis( l-hydroxyethyl)benzene (in the form of its diacetate ester) 61 m-( l-hydroxyethyl)ethyibenzene (mainly in the form of its acetate ester) 16 m-ethylacetophenone 21 7:- m-diacetylbenzene 2 Compared to those of Example XXVII, these results show that, by increasing the quantity of oxidant in comparison to the substrate and by extending the reaction time, it is possible to oxidize the two alkyl substituents of a dialkylaromatic compound.

EXAMPLE XXIX The experiment of Example XXVII was repeated except that the concentration of m-diethylbenzene was doubled (0. l0 mol/liter instead of 0.05). The reaction was extremely fast, since 77 percent of the manganic ions were reduced within 3 minutes.

The reaction mixture was then treated by an extraction method analogous to that applied in Example XXVI], and also analyzed by vapor phase chromatography. Analysis showed that percent of the m-diethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages m( l-hydroxyethyl )ethylbenzene (mainly in the form of its acetate ester) 96 m-bis( I-hydroxyethyl)benzene (mainly in the form of its diacetate ester) 3 m-ethylacetophenone l Compared to those of Example XXVI], these results show the gain in reaction rate and in selectivity achieved when increasing the amount of substrate compared to the oxidant.

EXAMPLE XXX This example illustrates the oxidation of m-diethylbenzene by means of the system consisting of manganic acetate and perchloric acid,

The experiment of Example XXVI] was repeated while substituting perchloric acid for sulphuric acid in the same concentration. 28 percent of the manganic ions had been reduced m-( l-hydroxyethyl)ethylbenzene (mainly in the form of its acetate ester) 97 m-bis( l-hydroxyethyl)benzene (in the form of its diacetate ester) traces m-ethylacetophenone 3 EXAMPLE XXXI This example illustrates the oxidation of m-diethylbenzene by means of the system consisting of cobaltic acetate and sulphuric acid.

A solution containing 0.05 moi/liter of m-diethylbenzene, 0.20 mol/liter of cobaltic acetate and 0.5 moi/liter of sulphuric acid in acetic acid was kept at 25 C. under a nitrogen atmosphere at atmospheric pressure. 44 percent of the cobaltic ions had been reduced after 20 minutes. The reaction mixture was then treated and analyzed as in Example XXVll. It was thus established that 55 percent of the m-diethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages I m-( l-hydroxyethyl)ethylbenzene (mainly in the form of its acetate ester) 70 m-bis( l-hydroxyethyl)benzene (in the form of its diacetate ester) 4 m-ethylacetophenone 24 m-( l-hydroxyethyl)acetophenone 2 EXAMPLE XXXII This example illustrates the oxidation of m-diethylbenzene by means of the system consisting of cobaltic acetate and phosphoric acid.

The experiment of Example XXXI was repeated while substituting phosphoric acid for sulphuric acid in the same concentration. 30 percent of the cobaltic ions had been reduced after ten minutes, and analysis showed that 39 percent of the m-diethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages m-( l-hydroxyethyl)ethylbenzene (mainly in the form of its acetate ester) 79 m-bis( lhydroxyethyl)benzene (in the form of its diacetate ester) 6 m-ethylacetophenone 15 EXAMPLE XXXIII This example illustrates the oxidation of m-diethylbenzene by means of the system consisting of cobaltic acetate and perchloric acid.

The experiment of Example XXXI was repeated while substituting perchloric acid at the concentration of 1.0 mol/liter for sulphuric acid. 47 percent of the cobaltic ions had been reduced after 10 minutes, and analysis showed that 79 percent of the m-diethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages m-( l-hydroxyethyl)ethylbenzene (mainly in the form of its acetate ester) 86 m-bis( l-hydroxyethyl)benzene (in the form of its diacetate ester) 4 m-ethylacetophenone l0 EXAMPLE XXXIV This example illustrates the oxidation of rn-diethylbenzene by the system consisting of cobaltic acetate and trichloroacetic acid.

The experiment of Example XXXI was repeated while substituting trichloroacetic acid at the concentration of 1.5 moi/liter for sulphuric acid. 23 percent of the cobaltic ions had been reduced after 30 minutes, and analysis showed that 42 percent of the m-diethylbenzene employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages m-( l-hydroxyethyl)ethylbenzene (mainly in the form ofits acetate ester) m-bis( l-hydroxyethyl)benzene (in the form ofits diacetate ester) 3 m-ethylacetophenone 7 74 By operating in the same conditions but in the absence of trichloroacetic acid, only 10 percent of the cobaltic ions were reduced after 2 hours (this being a period which is four times as long as in the experiment hereinabove) and only 9 percent of the m-diethylbenzene was converted to yield the following products m-( l-hydroxyethyl )ethylbenzene (in the form of its acetate ester) m-ethylacetophenone Hereagain. it is apparent that in the absence of the acid activator, the reaction is not only slowed down considerably, but its selectivlity is changed completely.

EXAMPLE XXXV m-ethylacetophenone 66 m-( l-hydroxyethyl)ethylbenzene l7 acetate es ter of m-( l-hydroxyethyl)ethylbenzene l6 m-bis( l-hydroxyethyl)benzene l By continuing the same experiment up to 24 hours, 57 percent of the cobaltic ions were reduced and 89 percent of the m-diethylbenzene employed was converted to yield the following products m-ethylacetophenone 73 m-( l-hydroxyethyl)ethylbenzene 2 acetate es ter of m-( l-hydroxyethyl)ethylbenzene 1O m-bis( l-hydroxyethyUbenzene 5 m-( l-hydroxyethyl)acetophenone 3 m-diacetylbenzene 7 By comparing these results to those of Example XXXIV, it is apparent that in the presence of oxygen the hydrocarbon is oxidized preferentially into ketone rather than into alcohol.

EXAMPLE XXXVI This example illustrates the oxidation of the acetate of ml-hydroxyethyl)ethylbenzene by means of the system consisting of cobaltic acetate and phosphoric acid.

A solution containing 0.05 mol/liter of the acetate of m-( lhydroxyethyl)ethylbenzene, 0.10 mol/liter of cobaltic acetate and 1.0 mol/liter of phosphoric acid was kept at 25 C under a nitrogen atmosphere at atmospheric pressure. 43 percent of the cobaltic ions had been reduced after 4 hours. The reaction mixture was then treated by an extraction method analogous to that employed in Example XXVII and the extract was also analyzed by vapor phase chromatography. It was thus established that 25 percent of the ester employed had been converted to yield the following oxidation products whose relative proportions are expressed as molar percentages m-bis( l-hydroxyethyl)benzene (mainly in the form of its diacetate ester) 9 methylacetophenone m-( 1-hydroxyethyl)acetophenone Mum usa e EXAMPLE XXXVII This example illustrates the oxidation of durene by means of the system consisting of cobaltic acetate and trichloroacetic acid.

A solution containing 0.05 mol/liter of durene, 0.30 moi/liter of cobaltic acetate and 1.5 mol/liter of trichloroacetic acid in acetic acid was stirred at 60 C. in the presence of pure oxygen under a pressure of 10 kg/cm 78 percent of the cobaltic ions had been reduced after 24 hours. After evaporation of the solvent, the acidic products were separated by extraction with aqueous potash followed by acidification with hydrogen chloride; they were then analyzed by paper chromatography. It was thus established that durene had been quantitatively converted to yield the following oxidation products whose relative proportions are expressed as molar percentages durylic acid 4 dimethylphthalic acids 68 methyltrimellitic acid 23 7o pyromellitic acid 5 What is claimed is 1. The process of oxidizing an alkylaromatic compound having at least one alkyl radical with at least one hydrogen atom in the alpha position relative to the aromatic nucleus, which process comprises reacting said compound in the liquid phase with a metal compound selected from the group consisting of a trivalent cobalt salt, a trivalent manganese salt and mixtures thereof, in the presence of an activator selected from the group consisting of the acids having a dissociation constant higher than 10 and which are stable in the conditions of the reaction, boron trifluoride, and mixtures thereof, at a temperature between 30 and +1 C.

2. The process as defined in claim 1 wherein the aromatic nucleus of said alkylaromatic compound is selected from the group consisting of benzene and naphthalene.

3. The process as defined in claim 2 wherein said aromatic nucleus has from l to 6 alkyl substituents, each having from one to four carbon atoms.

4. The process as defined in claim 2 wherein said aromatic nucleus is further substituted with a polar radical selected from the group consisting of halo, nitro, acyl, l-acyloxyalkyl, carboxy and alkoxy.

5. The process as defined in claim 1 wherein the metal compound is carboxylate.

6. The process as defined in claim wherein said carboxylate is the salt of a fatty acid having from two to 10 carbon atoms.

7. The process as defined in claim 6 wherein the metal salt is an acetate.

8. The process as defined in claim 1 wherein said activator is selected from the group consisting of sulphuric, perchloric, ptoluenesulphonic, trifluoroacetic, trichloroacetic, tribromoacetic, dichloroacetic, phosphoric and monochloroacetic acid, boron trifluoride, and mixtures thereof.

9. The process as defined in claim I wherein the reaction is efiected in the presence of a solvent selected from the group consisting of the fatty acids having from two to 10 carbon atoms, and the methyl and t-butyl esters of said fatty acids.

10. The process as defined in claim 9 wherein the said solvent is acetic acid.

11. The process of oxidizing an alkylaromatic compound having at least one alkyl radical with at least two hydrogen atoms in the alpha position relative to the aromatic nucleus, to selectively produce an ester, comprising reacting said alkylaromatic compound with a carboxylate of a metal selected from the group consisting of trivalent cobalt and trivalent manganese in the presence of a fatty acid solvent having from two to l0 carbon atoms and of an activator selected from the group consisting of the acids having a dissociation constant higher than 10 and which are stable in the conditions of the reaction, boron trifluoride, and mixtures thereof, at a temperature between 30 and +1 00 C., in an atmosphere free of molecular oxygen.

12. The process as defined in claim 11 wherein the aromatic nucleus of said alkylaromatic compound is selected from the group consisting of benzene and naphthalene.

13. The process as defined in claim 12, wherein said aromatic nucleus has from I to 6 alkyl substituents each having from one to four carbon atoms.

14. The process as defined in claim 12 wherein said aromatic nucleus is further substituted with a polar radical selected from the group consisting of halo, nitro, acyl, lacyloxyalkyl, carboxy and alkoxy.

15. The process as defined in claim 1] wherein said carboxylate is the salt of a fatty acid having from two to 10 carbon atoms.

16. The process as defined in claim 15 wherein the metal salt is an acetate.

17. The process as defined in claim 11 wherein said activator is selected from the group consisting of sulphuric, perchloric, p-toluenesulphonic, tritluoroacetic, trichloroacetic, tribromoacetic, dichloroacetic, phosphoric and monochloroacetic acid, boron trifluoride, and mixtures thereof.

18. The process as defined in claim 11 wherein said fatty acid solvent is acetic acid.

19. The process as defined in claim 1 wherein the alkylbenzene is toluene and the oxidation product is a member of the group consisting of the esters of benzyl alcohol, benzaldehyde and benzoic acid.

20. The process as defined in claim 1 wherein the a1kylbenzene is ethylbenzene and the oxidation product is a member of the group consisting of the esters of the alphamethylbenzyl alcohol, and acetophenone.

21. The process as defined in claim 1 wherein the alkylbenzene is a xylene and the oxidation product is a member of the group consisting of the esters of methylbenzyl alcohol, and of xylylene, diol, methylbenzaldehyde, toluic acid, phthalic acid, isophthalic acid and terephthalic acid.

22. The process as defined in claim 1 wherein the alkylbenzene is diethylbenzene and the oxidation product is a member of the group consisting of the esters of (l-hydroxyethyl )ethylbenzene and of bis(l-hydroxyethyl benzene; ethylacetophenone and diacetylbenzene.

23. The process as defined in claim 11 wherein the alkylbenzene is toluene and the oxidation product is an ester of benzyl alcohol.

24. The process as defined in claim 11 wherein the alkylbenzene is ethylbenzene and the oxidation product is an ester of alpha-methylbenzyl alcohol.

25. The process as defined in claim 11 wherein the alkylbenzene is diethylbenzene and the oxidation product is a member of the group consisting of the esters (l-hydroxyethyl)-ethylbenzene and of bis( l-hydroxyethyl)benzene. 

2. The process as defined in claim 1 wherein the aromatic nucleus of said alkylaromatic compound is selected from the group consisting of benzene and naphthalene.
 3. The process as defined in claim 2 wherein said aromatic nucleus has from 1 to 6 alkyl substituents, each having from one to four carbon atoms.
 4. The process as defined in claim 2 wherein said aromaTic nucleus is further substituted with a polar radical selected from the group consisting of halo, nitro, acyl, 1-acyloxyalkyl, carboxy and alkoxy.
 5. The process as defined in claim 1 wherein the metal compound is carboxylate.
 6. The process as defined in claim 5 wherein said carboxylate is the salt of a fatty acid having from two to 10 carbon atoms.
 7. The process as defined in claim 6 wherein the metal salt is an acetate.
 8. The process as defined in claim 1 wherein said activator is selected from the group consisting of sulphuric, perchloric, p-toluenesulphonic, trifluoroacetic, trichloroacetic, tribromoacetic, dichloroacetic, phosphoric and monochloroacetic acid, boron trifluoride, and mixtures thereof.
 9. The process as defined in claim 1 wherein the reaction is effected in the presence of a solvent selected from the group consisting of the fatty acids having from two to 10 carbon atoms, and the methyl and t-butyl esters of said fatty acids.
 10. The process as defined in claim 9 wherein the said solvent is acetic acid.
 11. The process of oxidizing an alkylaromatic compound having at least one alkyl radical with at least two hydrogen atoms in the alpha position relative to the aromatic nucleus, to selectively produce an ester, comprising reacting said alkylaromatic compound with a carboxylate of a metal selected from the group consisting of trivalent cobalt and trivalent manganese in the presence of a fatty acid solvent having from two to 10 carbon atoms and of an activator selected from the group consisting of the acids having a dissociation constant higher than 10 3 and which are stable in the conditions of the reaction, boron trifluoride, and mixtures thereof, at a temperature between -30* and +100* C., in an atmosphere free of molecular oxygen.
 12. The process as defined in claim 11 wherein the aromatic nucleus of said alkylaromatic compound is selected from the group consisting of benzene and naphthalene.
 13. The process as defined in claim 12, wherein said aromatic nucleus has from 1 to 6 alkyl substituents each having from one to four carbon atoms.
 14. The process as defined in claim 12 wherein said aromatic nucleus is further substituted with a polar radical selected from the group consisting of halo, nitro, acyl, 1-acyloxyalkyl, carboxy and alkoxy.
 15. The process as defined in claim 11 wherein said carboxylate is the salt of a fatty acid having from two to 10 carbon atoms.
 16. The process as defined in claim 15 wherein the metal salt is an acetate.
 17. The process as defined in claim 11 wherein said activator is selected from the group consisting of sulphuric, perchloric, p-toluenesulphonic, trifluoroacetic, trichloroacetic, tribromoacetic, dichloroacetic, phosphoric and monochloroacetic acid, boron trifluoride, and mixtures thereof.
 18. The process as defined in claim 11 wherein said fatty acid solvent is acetic acid.
 19. The process as defined in claim 1 wherein the alkylbenzene is toluene and the oxidation product is a member of the group consisting of the esters of benzyl alcohol, benzaldehyde and benzoic acid.
 20. The process as defined in claim 1 wherein the alkylbenzene is ethylbenzene and the oxidation product is a member of the group consisting of the esters of the alpha-methylbenzyl alcohol, and acetophenone.
 21. The process as defined in claim 1 wherein the alkylbenzene is a xylene and the oxidation product is a member of the group consisting of the esters of methylbenzyl alcohol, and of xylylene, diol, methylbenzaldehyde, toluic acid, phthalic acid, isophthalic acid and terephthalic acid.
 22. The process as defined in claim 1 wherein the alkylbenzene is diethylbenzene and the oxidation product is a member of the group consisting of the esters of (1-hydroxyethyl )ethylbenzene and of bis(1-hydroxyethyl ) benzene; ethylacetophenone and diacetylbenzene.
 23. The process as defined in claim 11 wHerein the alkylbenzene is toluene and the oxidation product is an ester of benzyl alcohol.
 24. The process as defined in claim 11 wherein the alkylbenzene is ethylbenzene and the oxidation product is an ester of alpha-methylbenzyl alcohol.
 25. The process as defined in claim 11 wherein the alkylbenzene is diethylbenzene and the oxidation product is a member of the group consisting of the esters (1-hydroxyethyl)-ethylbenzene and of bis(1-hydroxyethyl)benzene. 